Charles clamond



(No Model.

0. CLAMOND.

MICROPHONE. No. 486,244. Patented Nov.15,'1 892.

ZZZ/67230 CZarZes 6702207202 I mm-mirm UNITED STATES CHARLES OLAMOND,

PATENT OFFICE.

OF PARIS, FRANCE.

MICROPHONE.

SPECIFICATION forming part of Letters Patent No. 486,244, dated November 15, 1892.

Application filed March 21, 1892.

To all whom it may concern:

Be it known that I, CHARLES CLAMOND, a citizen of the Republic of France, and a resident of Paris, in the Department of the Seine, Republic of France, have invented certain new'and useful Improvements in Microphones, of which the following is a specification.

My invention has reference to improvements in the method of and apparatus for. telephonic transmission; and it also embraces special improvements in telephonic transmitters of that class in which the vibrations of the air which accompany the utterance of sound produce electrical undulations similar in form to the sound-waves by variations of electrical resistance in a charged electric circuit. Instruments of this character have been called variable-resistance telephones, and the variation of resistance was heretofore produced, mainly, in two ways. The principal method was to vary the contact and pressure between two or more discrete bodies inserted in an electric circuit, and these bodies were then called the telephonic electrodes. Another method of varying the resistance of the circuitwas to use one solid and one fluid electrode, both of comparatively-high resistance,

and to partly immerse the solid electrode in the fluid and to vary the extent of immersion by the action of sound-waves. By the first method great variations of electrical resistance were obtained; but these variations were not always exactly proportionate to the amplitndes of the sound waves, whereby the quality of the sound uttered against the instrument became somewhat modified in the receiver. Another difficulty in this mode of telephonic transmission was that it was difficult to maintain the electrodes at all times in contact, and when the latter was broken and again established it gave rise to such violent electrical impulses, which had no relation to the sound-waves which produced the same, as to cause in the receiver a very loud and disagreeable sound, which rendered the speech or other sounds which it was intended to transmit sometimes inaudible or so blended with the accidental sounds caused by the makes and breaks as to make the speech unintelligible. By the second method of telephonic transmission the variations of electrical resistance produced were weak. The electrical Serial No. 425,729. (No model.)

undulations therefore were very faint, and consequently the reproduced sounds, while they were very clear, were almost inaudible.

It is the object of my invention to overcome these difficulties, and I do overcome the same by resorting to a mode ofproducing great variations of electrical resistance by soundwaves which are accurately proportionate to the amplitudes of said sound-waves without at any time breaking the circuit. By my method therefore the advantages of the two old methods are combined, while the disadvantages of the same are completely avoided. I accomplish this result by connecting permanently with two electrodes of the telephonic circuit and between the same a plastic semi-fluid electrical resistance which at all times completely bridges the two electrodes, which at no time varies the resistance of transition between itself and either of the electrodes, but which varies its shapethat is to say, its length and cross-sectionunder the influence of sound-waves, and thereby varies the electrical resistance of the circuit. The variations which I thus produce I have found to be very accurately proportionate to the amplitudes of the sound-waves and to be very great. All this will more fully appear from the following detailed description, in which reference is made to the accompanying drawings, in which I have illustrated some of the forms of apparatus suitable for the r ctice of my invention, and in which- Figures 1, 2, and 3 represent the elecotrdes with the variable resistance interposed and varied in shape corresponding to different phases of operation,the whole included in an electric circuit. Fig. 4 is a vertical section of a telephone-transmitterembodying my i11- vention included in a working circuit. Figs. 5 and 6 are longitudinal sections showing two forms of electrodes with the plastic variable resistance interposed, and Fig. 7 is a vertical section of another form of telephonic transmitter embodying my invention and included in a working circuit.

Like numerals of reference indicate like parts all throughout the drawings.

The principle element of the apparatus is a plastic pasty electrical conductor, which consists of an intimate mixture of a finelydivided solid and of a liquid,'constituting as a whole a plastic viscid pasty body of such consistence as is sometimes called a semifluid. The plasticity may be due either entirely to the fluid or to the mixture of the fluid with the solid, and the conductivity may also be due either to the solid or to the fluid, or to both, and I am not confined to any particular fluid or to any particular solid in the composition of my improved telephonic resistance. Thus I might use ordinary potters clay, the plasticity of which is due to a particular property of silicate of alumina in contact with water and the conductivity of which is due to both the silicate of alumina and the water. By preference, however, my improved telephonic resistance is not made of native compounds, but is artificially compounded. Good results are obtained by mixing concentrated solutions of saltssuch as solutions of silicate of soda, silicate of potash, chloride of calcium, or acetate of magnesia-with powders of either conducting or non-conducting bodies in suflicient quantities to make aviscid plastic body of such consistence that it will notflow spontaneously, butwill resist only very lightly the action of forces tending to distort their shapes. Such compounds, in which the powd ers employed maybe of metal or of carbon or oxides of metals, or of any non-conducting substance, undergo a considerable change when used for some time in telephonic transmission on account of the electrolytic action of the current upon the salt solution, and for this reason I prefer to employ for commercial use pastes in which no electrolytic action takes place. This result I obtain by mixing conducting-powders with sirupy and viscid liquids which are non-conductors of electricity, such as glycerine, viscid oils, like castor-oil, or a plastic viscid body, such as Vaseline. In addition to the powders already specified I may use the powders of metallic alloys, or I may use conducting-metalloids, such as tellurium, silicium, or binary combinations of conductors which are easily pulverized, such as certain sulphides or oxides of metal; but I give the preference to metals, simple or alloyed, and to metalloids which are not decomposed by the current, and among these metals or alloys or metalloids I use, by preference, those which give powders having the least weight, for the lighter the elements of the paste are the lighter the whole mass and the more readily can its form be changed by the action of sonorous waves upon the same.

In Fig. 1 a plastic viscid button made in accordance with my inventionis represented at 1. It may, as shown, have the shape of a short but rather thick cylinder. 2 and 3 represent the terminals of an electric circuit charged by a battery 4, with which the terminals are connected by the wires 5 6, and a galvanometer or other current-indicator 7 is also included in the circuit. If one of these terminals 2 3 is fixed and the other is free to move axially under the action of sound-waves,

then the arrangement shown in Fig. 1 becomes a telephonic transmitter constructed upon the principle of my invention. The resistance-changer 1, being pasty, adheres at.

each end to one of the electrodes, and if one of these electrodes moves axially toward or from the other the shape of the resistance changer, which for convenience of description may be called a microphonic element, changes. If, for instance, one of the electrodes approaches the other under the action of sound-waves, the microphonic element 1 becomesshorterandthicker,andconsequently its electrical resistance, and therefore that of the circuit, is decreased. This phase of operation is represented in Fig.2. If, on the other hand, one of the electrodes recedes from the other under the action of sound-waves, the microphonic element becomes elongated, as shown in Fig. 3, and assumes ahyperboloidal formthat is to say, a shape resembling two truncated cones joined at their small ends, as represented in Fig. 3. The microphonic element therefore has increased in length and decreased in thickness, whereby its electrical resistance and that of the circuit is increased. The galvanometer 7, included in the circuit, will indicate an increased amount of current under the conditions shown in Fig. 2 and a decreased amount of current under the conditions shown in Fig. 3. While such variations of the total resistance of the body of the microphonic element take place no variation of resistance takes place at the surfaces at which the microphonic elementis connected with the electrodes 2 and 3-that is to say, the transition resistance for the passage of the current from electrode 2 to the microphonic element 1 and the transition resistance to the passage of the current from the microphonic element to the electrode 3 remains constant during all phases of operation. since by reason of the pasty nature of the microphonic element the contact of the same with the electrodes is not varied whether these electrodes approach to or recede from each other.

Fig. 4. represents one practical form of transmitter embodying my invention. The cylindrical casing 8 has mounted at its open end the diaphragm 9, which in this case is of resonant conducting material, and this diaphragm has secured to its center the electrode 2. A second electrode 3 is supported by a bracket 10, which is secured to the casing, as shown. Between the two electrodes and adhering to each of the same is my improved microphonic element 1, and a very thin sleeve 11, of elastic non-conductingmaterial-like soft rubber or collodionsurrounds the microphonic contact and a portion of each electrode, the purpose of which is to maintain the normal shape of the microphonic element in all positions of the instrument and to protect that element against violent distortion, which might otherwise be caused by violent shocks which the instrument may receive of the battery to wire 14 to the primary coil 15 of an inductorium, and from the latter by wire 16 to the diaphragm. The secondary of the inductorium is included in the line 17, in which the receiving-telephone 18 is placed. For short lines the induction-coil may be omitted, and the telephone-receiver is then placed in the battery-circuit.

In the apparatus shown in Figs. 4 and 5 the electrodes and the microphonic element are represented cylindrical in form 5 but this form is not essential, nor am I confined to any particular form of either the electrodes or of the microphonic element; but the form which 'I prefer and which I have found very effective is that represented in Fig.6. In

this case one of the electrodes 2 is a cylindrical body shaped convex, semispherical at one end, while the other electrode 3 is a viscid, and plastic microphonic element 1,.

which thus assumes the shape of a thimble or, approximately, of a semispherical shell. The thin elastic non-conducting sleeve 11 covers a portion of each electrode and the otherwise exposed surface of the microphonic element. This construction may be used in the apparatus shown in Fig. 4, in which case the electrode 2 would be made fast to the center of the diaphragm, while the electrode 3 could be fixed to the bracket 10. By preference, however, these two electrodes, with the intervening microphonic element, are supported in the manner shown in Fig. 7that is to say, the electrode 2 is suspended by a spring or wire 19 and the electrode 3 by a spring or wire 20- and both of them are urged toward the diaphragm by a leaf-spring 21, the tension of which may be adjusted by the screw 22. The outer end of electrode 2 is in this case made conical, as indicated in Fig. 6 at 2', and the point of this cone is maintained in contact with the center of the diaphragm, which in this case may be of insulating material, such as mica, for instance. The circuit connections are or may be the same as those described with reference to Fig. 4, the wires 13 and 16 in this case connecting with the suspension springs or wires 20 and 19, respectively.

From the foregoing description it will appear that my novel method of transmitting vocal and other sounds telegraphically consists in varying by and in accordance with sound-vibrations the cross-section and the length of a conductor included in the telephonic circuit, and thereby producing electri cal undulations similar in form to the soundwaves which accompany the utterance of said vocal and other sounds. It will furthermore be clear that I can practice this method of telephonic transmission by means of a great variety of apparatus, and that while I have hereinbefore shown and described some apparatus adapted for the practice of my method I am not confined to the use of any particular apparatus or means.

Having now fully described my invention, I claim and desire to secure by Letters Patent- 1. The method of transmitting vocal and other sounds telegraphically by causing said sounds to vary the cross-section and length and corresponding electrical resistance of an electrical conductor included in a charged electric circuit, and thereby, producing electrical undulations similar in form to thesoundwaves which accompany the utterance of said vocal and other sounds, substantially as described. V

2. A telephonic transmitter comprising two electrodes at a distance from each other and a plastic viscid conducting body maintained in invariable contact with the two electrodes, the whole included in a charged electric circuit, substantially as described.

3. Atelephonic transmitter comprising two separated electrodes forming the terminals of a charged electric circuit, a plastic viscid conducting body maintained in invariable contact with the two electrodes,'and an elastic non-conductin g sleeve enveloping the plastic body, substantially as described.

4;. A telephonic transmitter comprising one fixed electrode and one electrode movable toward and from the other under the influence of sound-waves, a plastic viscid conducting body maintained in invariable contact with the two electrodes, a diaphragm for receiving the impact of sound-waves and giving' motion to the movable electrode, and a charged electric circuit including in series the two electrodes and the plastic viscid conductor, substantially as described.

5. In a telephonic transmitter, the combination of a diaphragm and an electrode receiving motion from said diaphragm, with another electrode separated from the first, a plastic viscid conductor maintained in invariable contact with the two electrodes, an elastic non-conducting sleeve enveloping the plastic conductor and a portion of the electrodes, and a charged electric circuit terminating at the electrodes, substantially as described.

6. In a telephonic transmitter, the combination of an electrode having a convex surface and a second electrode having a concave surface embracing but out of contact with the convex surface of the first electrode, and a plastic viscid conductor bridging the two electrodes and in invariable contact with the same, substantially as described.

7. In a telephonic transmitter, the combination of an electrode having a convex spherical surface and another electrode having a spherical cavity larger in diameter, but concentrically arranged with reference to the first electrode, and a plastic viscid conductor bridging the two electrodes and in invariable contact with their spherical surfaces, substantially as described.

8. A microphonic element consisting of a plastic viscid conductor, substantially as described.

9. A microphonic element consisting of a viscid plastic conductor composed of an intimate mixture of a fluid and of finely-divided solids, either or both of which are conductors of electricity, substantially as described.

10. A microphonic element consisting of a viscid plastic conductor of electricity, composed of an intimate mixture of a non-conducting fluid or fluids with finely-divided conducting solids, substantially as described.

11. A microphonic element consisting of a viscid and plastic conductor of electricity, composed of an intimate mixture of a viscid non-conducting fluid with finely-divided metal or metals or metalloids, substantially as described.

12. A viscid and plastic microphonic element consisting of an intimate mixture of glycerine and finely-divided metal or metals or metalloids, substantially as described.

In testimony whereof I have signed my name to this specification in the presence of two subscribing witnesses.

CHARLES CLAMOND.

Witnesses:

O. KERN, RoB'r. M. 1100mm. 

